Printing systems incorporating a gas flow are known, see, for example, U.S. Pat. No. 4,068,241, issued to Yamada, on Jan. 10, 1978.
The device that provides gas flow to the gas flow drop interaction area can introduce turbulence in the gas flow that may augment and ultimately interfere with accurate drop deflection or divergence. Turbulent flow introduced from the gas supply typically increases or grows as the gas flow moves through the structure or plenum used to carry the gas flow to the gas flow drop interaction area of the printing system.
Drop deflection or divergence can be affected when turbulence, the randomly fluctuating motion of a fluid, is present in, for example, the interaction area of the drops (traveling along a path) and the gas flow force. The effect of turbulence on the drops can vary depending on the size of the drops. For example, when relatively small volume drops are caused to deflect or diverge from the path by the gas flow force, turbulence can randomly disorient small volume drops resulting in reduced drop deflection or divergence accuracy which, in turn, can lead to reduced drop placement accuracy.
Turbulence reduction can be achieved by reducing the magnitude of disturbances and instability in the fluid flow. Local cooling has been theorized to be an effective technology for turbulence suppression. Cooling of a fluid flow surface cools the flow boundary layer which in turn will slow the development of turbulence instability. Local cooling to suppress turbulence was also experimentally demonstrated in Russia during 1980's. (See for example, Dovgal, Levchenko, and Timofeev, (1990) “Boundary layer control by a local heating of a wall,” from IUTAM Laminar-Turbulent Transition, eds. D. Arnal and R. Michel, Springer-Verlag, pp. 113-121). U.S. Pat. No. 6,027,078, issued on Feb. 22, 2000, to J. D. Crouch and L. L. Ng, discloses aircraft boundary-layer flow control system incorporated a local heating for laminar flow.
However, one of the problems related to these types of turbulence reduction techniques is that each technique is concerned with external flow for an object, and thus can't be directly implemented in an internal flow through a channel that a printing system encounters.
Accordingly, a need exists to reduce turbulent gas flow in the gas flow drop interaction area of a printing system.